September 15, 2022
Hole-Forming Technology of High-Pressure Jet Grouting Wall in Sandy Pebble Layer
Jet grouting (or swing spray, fixed spray) pile wall must be the first hole, and then rotary spray. The hole is the basis of the jet grouting wall, it takes up the whole jet grouting construction above time. In order to make holes in all kinds of strata with the rotary jet walls, the best drilling method should be selected to complete the drilling in the shortest time. However, this is often not valued by water conservancy and hydropower constructors. They focus on the jet grouting process, and it is difficult to create the best benefits.
Water conservancy and hydropower projects have a considerable number of anti-seepage walls built on the sand pebble layer, sand pebble layer due to loose, uneven hardness, into a hole are very difficult. This paper discusses the small diameter hole forming technology of high-pressure jet grouting in sand pebble layer.
1. Rotary Drilling into Hole
Rotary drilling in the sand pebble layer into a hole has some difficulty, recently some new methods, but the cost is slightly higher.
1.1 Diamond Drilling
Diamond drilling is still very effective in the sand pebble layer, but it must be accompanied by high-quality mud wall protection, or AB plant glue flushing fluid, in order to obtain good results.
Well wall protection, not easy to collapse the hole, no casing. Although high-pressure jet grouting does not require coring, diamond coring drilling saves more energy than full-face drilling, which is conducive to improving drilling efficiency and can be used for high-pressure jet grouting of dam foundation cutoff wall.
1.2 Diamond Carbide Composite Tooth Drill Bit Drilling
The composite tooth consists of a superhard layer and a support layer. The spherical crown is a superhard layer composed of synthetic diamond single crystal and WC-co cemented carbide, and the support layer is ordinary cemented carbide. Due to the high hardness and wear resistance of the superhard part of the composite cylindrical tooth, the spherical crown tooth top structure enables the composite tooth to withstand strong impact; at the same time, the matrix has high strength and impact resistance, which supports and protects the superhard part, and is conducive to the inlay and welding of the composite teeth. This form of drill bit drilling sand pebble layer is very effective. Back footage can be increased by 1 time, pure drilling efficiency increased by more than 15 times, and drilling costs can be reduced by 35% (compared with octagonal carbide drill).
2. Drilling with Pipe
There are two kinds of down-the-hole hammers with pipe drilling technology: one is the eccentric bit with pipe drilling, and one is a concentric bit with pipe drilling. All adopt the ball tooth hard alloy drill bit, above the drill bit is connected with the impact ring, then the upper part is connected with the down-the-hole hammer. The impact ring is located on the casing bit. After starting the DTH hammer, the impact ring hits the casing bit while the ball-tooth cemented carbide bit is drilling. After reaching the design depth, as long as the eccentric drill bit is reversed, you can get out of the drill. Then put PVC pipe in the casing. Then pull out the casing. The rotary jet machine can be immediately positioned, down the spray pipe for the rotary jet. The energy of the high-pressure jet is sufficient to break the PVC pipe so that the cement slurry can be injected into the formation and mixed.
3. High Jet Vibration Hole
The drilling principle of high-pressure jet grouting is the drilling principle of top-driven vibration impact rotation. The vibration hammer and hydraulic power head are installed at the top of the viaduct, but the process has changed greatly, making full use of the characteristics of non-coring, and combining the drilling and jet grouting organically. The double drill pipe is also a slurry pipe and a gas pipe. After the borehole reaches the design depth, it can be continuously sprayed and grouted without pulling out, which brings a qualitative leap to the construction of the whole high-pressure grouting cut-off wall.
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